Method of producing oxetane esters

ABSTRACT

DISCLOSED HEREIN ARE METHODS FOR PRODUCING BICYCLIC ORTHO ESTERS AND THEIR ISOMERS, OXETANE ESTERS. BICYCLIC ORTHO ESTERS ARE PREPARED BY DIRECT ESTERIFICATION OF TRIMETHYLOALKANES WITH CERTAIN MONOCARBOXYLIC ACIDS. THE BICYCLIC ORTHO ESTER CAN BE CONVERTED TO THE OXETANE ISOMER BY HEATING AT A TEMPERATURE OF FROM 275*C. TO 525*C. IN THE PRESENCE OF AN ALUMINA ISOMERIZATION CATALYST.

United States Patent 3,577,438 METHOD OF PRODUCING OXETANE ESTERS BruceAllen Melaas, Corpus Christi, Tex., assignor to Celanese Corporation NoDrawing. Original application Oct. 31, 1963, Ser. No. 320,557, nowPatent No. 3,328,427, dated June 27, 1967. Divided and this applicationMar. 13, 1967, Ser.

Int. Cl. C07d 3/00 US. Cl. 260-333 1 Claim ABSTRACT OF THE DISCLOSUREThis is a divisional application Ser. No. 320,557, filed Oct. 31, 1963,which was issued as US. Patent 3,328,427 on June 27, 1967.

This invention relates broadly to the art of producing esters and, moreparticularly, to the production of bi cyclic ortho esters, and theirisomers oxetaue esters. Bicyclic ortho esters, may be represented by thegeneral formula:

I CH2-O R(I1-CH2OO-R CHz-O and the isomeric oxetane ester may berepresented by the general formula:

CHr-O-Hl-R' R(I3(IJH2 CHr-O Both of these isomeric forms will sometimeshereinafter be referred to generically as bicyclic ortho esters. In theabove formulas R represents a member of the group consisting of hydrogenand alkyl (including cycloalkyl), aralkyl, aryl and alkaryl radicals,and R has the same meaning as R and, in addition, hydroxyalkyl(monohydroxyalkyl) and alkenyl. Preferably, R represents an ethylradical. The method comprises heating, under certain specifiedconditions, a reaction mass containing essentially a dimethylol compoundrepresented by the general formula:

Where R and R have the same meanings as given above with reference toFormula I. The scope of the present invention also includes certainsubclasses and species of ortho esters that can be produced by themethod of the invention and which are believed to be new chemicalcompounds.

Illustrative examples of radicals represented by R in Formulas I, I-Aand II and in other formulas herein are those containing from 1 to notmore than about 18 carbon atoms, advantageously from 2 to carbon atoms,inelusive. More specific examples of radicals embraced by R are methylthrough octadecyl (both normal and isomeric forms), cyclopentyl,cyclohexyl, cycloheptyl, etc.; benzyl, phenylethyl, phenylpropyl,phenylisopropyl, and higher members of the homologous series of aralkyl"ice radicals; phenyl, biphenylyl or xenyl, naphthyl and other arylradicals containing not more than about 18 canbon atoms; and variousalkaryl radicals including tolyl, xylyl, ethylphenyl, propylphenyl,isopropylphenyl and butylphenyl. Illustrative examples of radicalsrepresented by R in the aforementioned formulas are the same as thosegiven above with reference to R and, in addition, the monohydroxyalkylradicals wherein the alkyl grouping is methyl through octadecyl (bothnormal and isomeric forms); and alkenyl radicals, e.g., vinyl,a-methylvinyl, B-methylvinyl a,-ethylvinyl and the propenyl throughoctadecenyl (both normal and isomeric forms) radicals. Preferably R isan ethyl radical and R is an alkyl or an alkenyl radical containing from1 to 10 carbon atoms, inclusive.

The dimethylol compounds represented by Formula II, and which also maybe described as monoesters of a polyol, can be prepared, for example,from a polyol, more particularly a trimethylolalkane, represented by thegeneral formula III GE -OH R( 1-OHTOH Ilia-OH where R has the samemeaning as given above with reference to Formula I.

The production of bicyclic ortho esters does not appear to have receivedmuch attention from prior investigators. H. W. Post, The Chemistry ofthe Aliphatic Orthoesters, American Chemical Society Monograph SeriesReinhold Publishing Corporation, New York, NY. (1943), gives acomprehensive review of the preparation, properties and reactions ofaliphatic ortho esters up to the year of publication, but nowherementions the bicyclic ortho esters. The orthoformate ester oftrimethylolethane (TME) 'Was prepared by Doering and Levy (1. Am. Chem.Soc. 77, 509 (1955)). They obtained this orthoformate ester in a yieldof only 7.7% by reacting ethyl orthoformate with trimethylolethane(TM-E) at 140 C. Barnes et al. (J. Org. Chem. 27, (1962)) prepared theorthoacetate ester of TME by hydrogenation of the correspondingorthotrichloroacetate. Only a small over-all yield was obtained.

The present invention is based on my discovery that bicyclic orthoesters of the kind embraced by Formula I can be prepared in good (oftenvery high) yields from trimethylolalkanes of the kind embraced byFormula by, for example, direct esterification (Modification A) with amonocanboxylic acid represented by the general formula R'-COH Where Rhas the same meaning as given above with reference to Formula I. Thetrimethylolalkane and the monocarboxylic acid are employed in a molarratio of at least one mole of the former per mole of the latter.Preferably, an excess of trimethylolalkane is used, e.g., from 1 to 15mole percent in excess of equimolar proportions. The reaction sequencewhen starting With a trimethylolalkane may be illustrated by thefollowing simplified equations:

Certain of the bicyclic ortho esters of this invention also can beprepared (Modification B) by reacting together (1) a trimethylolalkaneof the kind within the scope of Formula III and, for example, (2) atriester of a trimethylol alkane that is represented by the generalformula F CH C-R' l R-C-CH2O- -R' CH2O-CR' where R represents a memberof the group consisting of hydrogen and alkyl, aralkyl, aryl and alkarylradicals, and R represents a member of the group consisting of alkyl,alkenyl, aralkyl, hydroxyalkyl, aryl and alkaryl radicals. In carryingout this reaction the reactants of (1) and (2) are employed in a molarratio of at least /3 mole of the latter for each mole of the former; inother words, in at least the stoichiometric amount required to form themonoester of the trimethylolalkane of 1) by a transesterificationreaction. Preferably the triester embraced by Formula VII is employed inexcess of the stoichiometric amount required to form the aforementionedmonoester, e.g., from 1 to 60 mole percent in excess of the aforesaidstoichiometric amount.

In a manner similar to that described above with par ticular referenceto the use of a triester of a trimethylolalkane, there, of course, alsocan be employed a diester of a trimethylolalkane using two moles of suchdiester to only one of the unreacted polyol.

As a further alternative (modification C) to the procedures broadlydescribed above, one can separately prepare a monoester (i.e.,dimethylol compound) of the kind embraced by Formula II and thencyclicize this compound in accordance 'with this invention, and asillustrated by one of the examples which follow, to obtain the desiredbicyclic ortho ester. Since this technique requires the separateisolation of the monoester before it is converted to the ortho ester, itis not as economical as the other procedures and wherein the monoesteris formed in situ.

Regardless of the technique whereby the dimethylol compound (i.e.,monoester of a trimethylolalkane) is prepared, that is, whether it isformed in situ or separately prepared, it is essential in practicing thepresent invention that the reaction under heat be effected (1) underacidic conditions, more particularly in the presence of an acidiccatalyst, e.g., p-toluenesulfonic acid (PTSA); (2) under reducedpressure; (3) at a temperature sufficient to rermove combined water fromthe dimethylol compound and whereby one molecule of water is evolvedfrom each molecule of dimethylol reactant. Furthermore, the heating (4)should be correlated with the rate of formation of the bicyclic orthoester product and (5) should be maintained at the lowest temperatureconsistent with the formation of the said ortho ester at an optimumrate. When the ortho ester is isolated by distillation, a condensertemperature should be used that will separate the ortho ester but willnot separate the by-product water of reaction.

It was quite surprising and unobvious that a bicyclic ortho ester of thekind with which this invention is concerned could be prepared as brieflydescribed above and more fully hereafter, especially in view of theknown instability of polyols of the trimethylolalkane-type in thepresence of either basic or acidic catalysts.

By practicing this invention and whereby yields of over 80% of thebicyclic ortho ester have been obtained, decomposition of thetrimethylolalkane is not great. This unobvious result is believed to bedue to the fact that under the specified reaction conditions themonoester of the tri methylolalkane is more stable than thetrimethylolalkane itself. Taking trimethylolpropane (TMP) asillustrative of a trimethylolalkane, it may be mentioned that TMPreverts through the opposite of an aldol reaction at 40 C. and above.Surprisingly and unobviously TMP monoesters are not subject to a reversealdol reaction at an appreciable rate when compared to the rate of thereaction whereby the ortho esters are formed.

In practicing the present invention, it is essential that the reactionbe carried out under acidic conditions such as those imparted to thereaction mass by an acidic esterification (includingtransesterification) catalyst. A catalytic amount of such a catalyst isused, e.g., from, by weight, about 0.05% to about 3% based on the weightof the starting reactant or reactants. Illustrative examples of suchcatalysts that can be employed (either alone or admixed with each otherin any proportions) are, in addition to p-toluenesulfonic acid mentionedhereinbefore, the following: sulfuric acid, phosphoric acid,benzenesulfonic acid or any other acid having a boiling point higherthan that of the reaction mixture. Certain types of alumina also may beuseful as the catalyst. Acidic ion-exchange resins that will 'withstandthe aboveindicated temperature requirements of the catalyst also may beutilized.

When the bicyclic ortho ester is formed by a two-stage sequence asillustrated by Equations V and VI or by a transesterification reactionas hereinbefore described, the acidic catalyst need not be removed byneutralization or otherwise from the reaction mass before continuingwith the formation of the desired ortho ester. If desired or required,additional catalyst can be added while forming the regular esterincluding the monoester or while the bicyclic ortho ester is beingformed.

The reaction can be carried out, at least initially, in the presence orabsence of a solvent. Thus one may use, for example, a volatile(volatilizable), inert (substantially completely inert), liquid,reaction medium; and the reaction may be initiated, when usingModification A or B described above, while the reactants are containedin such a medium. By inert or substantially completely inert liquidmedium is meant one which is so inert or non-reactive toward thereactants and the reaction product under the reaction conditions that itwill not materially affect the course of the reaction or theconstitution of the reaction product. By liquid medium is meant onewhich is liquid at the temperature and pressure employed in effectingthe reaction. In other words the inert, liquid medium in which thereaction can be initiated may or may not be a liquid at room temperatureor at any other temperature below the reaction temperature. Preferably aliquid medium that is volatile without decomposition is employed.

Illustrative examples of volatile, liquid, inert, reaction media thatcan be used are: aromatic hydrocarbons, e.g., benzene, toluene, xylene,etc.; the various inert ethers, e.g., di-n-propyl ether, the mixednormal and isomeric diamyl ethers, methyl butyl ether, tetrahydrofuran,mdioxane, p-dioxane, pentamethylene oxide, etc.; the various ketonesincluding the dialkyl ketones (e.g., the normal and various isomericdibutyl and diamyl ketones, methyl butyl ketone, ethyl amyl ketone,etc.), methyl benzyl ketone, methyl phenyl ketone (acetophenone), etc.Other examples are the normal and branched-chain hydrocarbons whichazeotrope water such as n-heptane, 2,2,4- trimethylpentane, and/ orpentene, octane, etc.

The solvent or liquid reaction medium, as shown by the foregoingexamples, may be one that boils below about 200 C. at atmosphericpressure. In some cases, however (e.g., in the preparation of anorthostearate), it may be desirable or necessary to use a higher-boilingsolvent such as the phenyl ethers.

Another class of solvents in which the reaction may be effectedcomprises those capable of co-distilling with water but which cannot bereturned to the reaction vessel due to their solubility in water.Examples of such solvents are dimethylformamide, dimethyl sulfoxide andsimilar materials. The solvent does not necessarily have to be a liquidat room temperature nor does it have to have a boiling point less thanthat of the ortho ester. For example, the triester of the polyol beingconverted may comprise the solvent during the ortho-ester-formingreaction. Such a solvent may provide certain advantages, e.g., a greaterrate of reaction.

When using Modifications A or B there is first obtained a statisticaldistribution of the esters (mono, etc.). In general, the procedurethereafter is to first slowly strip off the liquid reaction medium(e.g., benzene), if employed. This liquid medium (solvent or diluent)advantageously, although not always necessarily, is removed underreduced pressure. Then the reaction mass is slowly distilled underreduced pressure Without neutralizing or otherwise removing the acidicesterification catalyst. The base or pot temperature first increases, asdistillation proceeds, to the boiling point of the regular monoester,for example, about 175 to about 185 C. in the case of TMPmonopropionate, and at which temperature the corresponding bicyclicortho ester begins to distill under reduced pressure and is continuouslycollected. As indicated hereinbefore, care should be exercised to keepthe temperature of the base during distillation as low as is consistentwith an appreciable bicyclic ortho esterforming reaction rate.

Distillation is continued under reduced pressure until substantially allwater obtained as a by-product of the reaction has been evolved.

The pressure may be reduced as distillation proceeds to the minimumrequired to isolate the desired bicyclic ortho ester. Because the orthoesters react with water, which is formed during the ring-closurereaction, one should use a partial condenser when this technique ofisolating the product is employed. In other words, a condensertemperature that will separate the ortho ester but 'will not separatethe water should be used. This temperature will depend, of course, uponthe pressure under which distillation is being effected. For example,condenser water at a temperature of about 26 27 C. proved verysatisfactory when distilling off the ortho esters at pressures of about2-10 mm. HgA.

The crude isolated product is then purified by one or morere-distillations, by conventional extraction or extractions with aselective solvent or solvents, by a combination of such means, or byother conventional technique used in purifying esters and other chemicalcompounds.

In order that those skilled in the art may better understand how thepresent invention can be carried into effect, the following examples aregiven by way of illustration and not by way of limitation. All parts andpercentages are by weight unless otherwise stated.

EXAMPLE 1 This example illustrates the preparation of 1-methyl-4-ethyl-2,6,7-trioxabicyclo (2.2.2) octane (TMP orthoacetate), the formulafor which is VIII oH2-0 A 1 to 1 mole ratio of TMP (4.0 moles) andacetic acid (4.0 moles) was heated in a benzene solvent (500 cc.) usinga p-toluenesulfonic acid (PTSA) catalyst (2.2 g.). The mixture wasrefluxed (at 85 to 100 C.) until the rate of water removal in aDean-Stark trap became negligible. The resulting reaction mass, afterstripping oil the benzene solvent was cooled and dissolved in water (500cc. to 1 liter). This aqueous solution was extracted three times withmethylene chloride and the methylene chloride layer drawn oil and dried.The use of the methylene chloride-water system enables separation of thebicyclic ortho ester from any unreacted TMP present and at least partialseparation from the regular monoand diacetate esters of TMP as well ascatalyst. Distillation of the dried extract followed and the TMPorthoacetate was collected, B.P. 85 C. at 8 mm. HgA. A 36 mole percentyield of the crude ortho ester, C H O was obtained. The pure ortho esterwas a solid, M.P. 4041 C.

The product was sweet-smelling and sublimed readily at room temperatureor slightly above. Elemental analysis: Calculated for C H O (percent):C, 60.7; H, 8.9. Found (percent): C, 60.3; H, 9.2. Mass spectrometeranalysis showed a large parent mass at 158. Infra-red absorptionspectrum showed no hydroxyl or carbonyl absorption and showedcharacteristic cyclic C--OC bond absorption in the skeletal region. Onwarming with aqueous ethanol (H SO catalyst) ethyl acetate was formed.

In the foregoing procedure the reaction sequence follows thatillustrated generically by Equations V and VI, and whereby anintermediate polyol monoester is first formed. This monoester is thendehydrated to yield the desired bicyclic ortho ester.

Examples 2, 3 and 4, which follow, illustrate the preparation of1,4-diethyl-2,6,7-trioxabicyclo [2.2.2] octane (TMP orthopropionate)using different modifications of the general procedure described inExample I and whereby, in general, higher yields of the desired bicyclicortho ester are obtained.

EXAMPLE 2 To a 2-liter round-bottomed flask was charged 535 g. TMPtripropionate (1.77 moles), with which was mixed 536 g. (4.0 moles) TMPand 3.0 g. PSTA (0.28 wt. percent based on reactants). The flask wassurmounted with an 8-tray Oldershaw column, a variable takeoff-type headand condenser receiver fitted for vacuum distillation. Vacuum wasapplied (3.0 to 4.0 mm. HgA) and heating commenced. When the basetemperature reached 187 C. the ortho ester began to distill and wascontinually collected from to 104 C. During this time the basetemperature increased to 233 C. The reflux ratio was varied from 9-1down to 41. A total of 575 g. distillate was collected, which distillatewas redistilled through an 8-tray Oldershaw column. A total of 491 g. ofproduct comprising TMP orthopropionate was collected, B.P. 83 C. at 4.0mm. HgA. The isolated yield of ester, C H O based on propionate moietycharged, was 52.7 mole percent. On redistillation the product gave thefollowing analysis. Calculated for C H O (percent): C, 63.3; H, 9.4.Found (percent): C, 62.7; H, 9.6, r1 1.4519, Sp.gr.4, 1.0696, F.P.=14-15C.

EXAMPLE 3 To a 2-liter round-bottomed flask were charged 536 g. TMP (4.0moles), 296 g. propionic acid (93%, 3.73 moles), 500 m1. benzene and 2.2g. PTSA (0.25 wt. percent based on reactants charged). The flask wasfitted with a l-ft. by l-in. Vigreux column and a modified Dean- Starkwater trap and condensers. The water takeoff rate became negligibleafter 4 hrs. at a reflux temperature of 97 to 100 C. The reaction masswas refluxed for one additional hour and left to stand for about 16 hrs.A total of 87 g. water containing 1.56 wt. percent propionic acid (1.36g., 0.018 mole) was obtained.

The reaction product at this stage contained no TMP orthopropionate asdetermined by gas-chromatographic (GC) analysis. It was charged to aflask surmounted with an 8-tray Oldershaw column and a modified Claisenhead. The PTSA catalyst was not neutralized or removed. The benzene wasstripped off and the product phase collected, B.P. 68 to 126 C. at 2 to3 mm. HgA. Care was exercised not to exceed C. in the base. This wasregulated by decreasing the heat input as the distillation was beingcarried out. A residue of 61 g. remained as a thick yellow-brown syrup.A total of 572 g. distillate was collected, which distillate was 92 wt.percent of product comprising TMP orthopropionate (532 g., 3.09 moles).The major component other than the desired product in the distillate wasa regular TMP ester, probably TMP monopropionate. The efliciency toisolated ester C H O was 83.4 mole percent (based on the amount ofpropionic acid converted).

In a similar experiment an 81 mole percent yield was obtained. Theisolated product, however, was 99 wt. percent product. This improvementwas accomplished through the use of a variable takeoff head. The maximumbase temperature during the distillation of product was 188 C.

EXAMPLE 4 In a 2-liter round-bottomed flask were mixed 536 g. TMP (4.0moles), 296 g. propionic acid (93 wt. percent, 3.73 moles) and 2.2 g.PTSA (0.25 wt. percent based on the reactants). The flask was placedbeneath an 8-tray Oldershaw column, a swinging bucket variable takeoffhead and a condenser receiver fitted for vacuum distillation. Heatingwas commenced and the water-propionic acid azeotrope taken overhead at a40% takeoff rate. During this time the base temperature increased from122 to 164 C. A total of 74 g. distillate containing 11.9 wt. percentpropionic acid (8.8 g., 0.119 mole) was obtained.

At this stage vacuum was applied and, at 40% takeoff rate, product wascollected up to 76 C. at 2.1 mm. HgA. The base temperature rose quicklyfrom 92 to 177 C. (10 cc. distillate collected) and then more slowly to181 C. (10 cc. distillate collected) and then more solwly to 181 C.Toward the end of the distillation the temperature was allowed to riseto 193 C. A total of 470 g. product was obtained. It contained 98 wt.percent C H O ester (2.67 moles) as determined by GC analysis. A residueof 185 g. remained and 86 g. water was collected during productdistillation which contained 3.8 wt. percent propionic acid (3.3 g.,0.04 mole). The isolated yield of C H O ester was 75 mole percent basedon the reacted propionic acid.

The TMP orthopropionates prepared as described under Examples 2, 3 and 4were obtained in good yields. No methanol (or methyl propionate) andvery little ethacrolein were obtained. Only about 10 to 15 g. oflow-boiling organic material was obtained. Where a reaction solvent,e.g., benzene, was employed, more than 50% of this low-boiling materialwas reaction solvent. The residue from the distillation containedhydroxyl groups, ester functions and a small amount of acid catalyst.The major high-boiler in the residue comprises the diester of a TMPmonoether. Diesters of monoethers of this general class may berepresented by the general formula where R and R have the same meaningas hereinbefore given with reference to Formula I and other formulas inthis case. The residue also undoubtedly contains some unetherified TMPesters.

The ether-esters embraced by Formula IX, including the symmetrical andunsymmetrical diesters of a monoether of a trimethylol alkane, e.g.,such diesters of the monoethers of trimethylolethane andtrimethylolpropane, are useful as chemical intermediates in all suchapplications where compounds containing a functional group or groups,e.g., a hydroxy group, are useful. For instance, they can be used as areactant in making synthetic resins by reaction with an aldehyde such asformaldehyde, acetaldehyde, acrolein, furfural, glyoxal and otheraldehydric materials. They also may be used as modifiers of syntheticresins or their partial condensation products, e.g., phenol-aldehyde,urea-aldehyde, melamine-aldehyde (including phenol-ureaandmelamine-formaldehyde) partial condensation products or resins.

EXAMPLE. 5

A monopropionate ester of TMP was prepared by reacting togetherequimolar proportions of propionic acid 8 and TMP using an ion-exchangeresin of the acidic type as an esterification catalyst, which resin wasthen removed by filtration. The crude product was heated to reflux underreduced pressure. The temperature of the vapors was that of the normalester mixture (133 C. at 1.5 mm. HgA). The monoester was then distilledand collected from 133 to 146 C. at 1.4 mm. HgA. The distillate was, inturn, distilled under ortho ester-forming conditions, for instance, inessentially the same manner as described under Example 4. After 10 cc.of monoester had been collected, PTSA catalyst (0.8 wt. percent) wasadded, whereupon the overhead temperature fell rapidly to 87- 88 C. at2.6 mm. HgA. TMP orthopropionate was then collected (based on GCanalysis). The atmospheric boiling point of TMP orthopropionate wasfound to be 220 to 221 C.

EXAMPLE 5 To a 2-liter round-bottom flask, fitted with a 1 foot by 1inch Vigreux column and a modified Dean-Stark water trap with suitableAllihn bulb condensers, were charged 536 grams TMP (4.0 moles), 209grams 88% formic acid (4.0 moles), 500 cc. benzene solvent and 3.0 gramsp-toluenesulfonic acid. After standing overnight the homogeneous mixturewas refluxed and the water, 101 grams collected. This water contained6.6 wt. percent formic acid by titration with standard caustic.

The solvent was then removed and the product comprising ortho estercollected, B.P. 142 to 150 C. at 4.0 to 8.5 mm. HgA. A total of 310grams of a thick syrup, which was a mixture of TMP orthoformate and theregular TMP esters was obtained. This crude product was sublimed and thewhite crystalline TMP orthoformate, grams, obtained. (Analysis: Calcdfor C H O (percent: C, 58.3; H, 8.3. Found (percent): C, 58.4; H, 8.5).Yield of pure C H 0 ester was 22.2 wt. percent on formic acid reacted;M.P.=60 C.

EXAMPLE 7 To a 2-liter round-bottom flask, fitted as in Example 3, wereplaced 480 g. technical grade trimethylolethane, 318 g. 93 wt. percentpropionic acid (4.0 moles), 2.0 g. p-toluenesulfonic acid and 473 cc.benzene. The esterification reaction was conducted in the normal manner.After water evolution was essentially complete, the benzene solvent wasremoved under reduced pressure and the distillation continued. A totalof 507 g. of product compris ing TME orthopropionate was collected, B.P.75 C. at 3.0 mm. HgA. The residue remaining weighed 114 g. The yield ofC H O ester obtained was 80.2 mole percent based on reactants charged.

This material was redistilled and pure product obtained, B.P. 60.5" C.at 3.0 mm. HgA. It had a RP. of 145 to C. Anal. calculated for C H O(percent): C, 60.7; H, 8.9. Found (percent): C, 60.7; H, 9.1. 11 1.4473,Sp.gr. 1.0837.

EXAMPLE 8 To a 2-liter round-bottom flask were charged 520 g.n-heptanoic acid (4.0 moles), 536 g. TMP (4.0 moles), 3.0 g.p-toluenesulfonic acid and 600 cc. benzene. No more water from theregular ester formation was observed after 3% hours. A total of 66 ml.water containing 0.2 wt. percent heptanoic acid was collected. A GCanalysis of the reactor product after the benzene solvent was removedshowed the presence of a small quantity of ortho heptanoate.

The crude ester mixture was then distilled under reduced pressure (3.2mm. HgA) and the C H O ester collected from 140 to 146 C. A total of 215g. (23.5% yield) was obtained that crystallized on standing. Thismaterial was recrystallized from n-pentane, yielding white needles; M.P.2930 C,

A nalysis.-Calculated for C I-1 0 (percent): 68.4; H, 10.6. Found(percent): C, 68.5; H, 10.8.

9 EXAMPLE 9 As per previous examples there were charged to a 2- literflask 536 g. TMP (4.0 moles), 408 g. pi-valic acid (4.0 moles), 500 cc.benzene and 3.0 g. p-toluenesulfonic acid and a TMP monopivalate mixtureprepare in the classical manner.

After stripping oil the solvent the product was heated below a 2-trayOldershaw column fitted with a Claisentype head. The product containingTMP orthopivalate was collected, B.P., up to 133 C. at 2 mm. HgA. Atotal of 622 g. of white solid (3.1 moles based on mol. wt. 214) wascollected. This amounts to a yield of 77.5 mole percent of C H O esterbased on acid and polyol originally charged. Water and decompositionproducts amounted to only 97.5 g. and the residue remaining afterdistillation was 114.5 g.

The crude C H O ester was extracted with diethyl ether and the etherremoved. The resulting white solid was recrystallized from n-pentane.Needles were obtained. M.P. 9494.5 C.

Analysis.Calculated for C H O (percent): C, 66.0; H, 10.1. Found(percent): C, 65.8; H, 10.4.

EXAMPLE Four moles each of trimethylolbutane (TMB) and propionic acidalong with 473 ml. benzene and 3.0 g. p-toluenesulfonic acid werecharged to a 2-liter flask. The monoester was formed in the usualmanner. After stripping off the solvent a total of 605 g. of colorlessproduct comprising TMB orthopropionate was collected, B.P. 92 C. at 3.0mm. HgA. This corresponds to an 81.4 mole percent yield of crude C H Oester based on the reactants charged.

This material was redistilled through a 1 m. Vigreux column, B.P. 103 C.at 5.0 mm. HgA, F.P. 24-25 C.

Analysis.-Calculated for C H O '(percent): C, 64.5; H, 9.7. Found(percent): C, 64.6; H, 9.8. 11 1.4517. Sp.gr. 1.0419.

EXAMPLE 11 Charged to a 2-liter flask were 536 g. TMP (4.0 moles), 378g. chloroacetic acid (4.0 moles), 500 cc. benzene and 3.0 g.p-toluenesulfonic acid. After forming the monoester and stripping thesolvent in the accepted manner the mixture was distilled under reducedpressure. There was collected 538 g. of product (B.P. 153 C. at 3.0 mm.HgA.) which, based on GC analysis, contained 75 mole percent of productcomprising orthochloroacetate. This represents a 52.5 wt. percent yieldbased on the reactants charged. A 256 g. residue remained.

This product was extracted with warm n-pentane, the extract cooled andthe pure C H O Cl ester filtered and dried under vacuum, yielding whiteneedles; MP. 53- 54 C.

Analysis.--Calculated for C H O (percent): C, 49.9; H, 6.8; Cl, 18.4.Found (percent) C, 50.1; H, 7.1; Cl, 18.1.

EXAMPLE 12 To a 1-liter round-bottom flask were charged 186 g. caproicacid (1.6 moles), 145 g. TMP (1.1 moles), 4.0 g. conc. H 80 and 473 cc.benzene. The crude product comprising TMP monocaproate mixture wasprepared in the classical fashion after which the solvent was removedunder reduced pressure. Distillation was continued and the orthocaproateproduct was collected from 112 to 134 C. at 3.0 mm. HgA. The crudeproduct amounted to 159 g. (46.2% yield), the residue weighing 87 g.

This crude C H O ester was recrystallized, M.P. 41.5- 42 C.

Analysis Calculated for C H C (percent): C, 67.3; H, 10.4. Found(percent): C, 66.8; H, 10.4.

Instead of the particular monocarboxylic acids employed in certain ofthe foregoing illustrative examples, one can use any othermonocarboxylic acid of the kind embraced by Formula IV includingbenzoic, phenylacetic (alphatoluic), ortho-, meta-, and para-toluic (ormixtures thereof), cyclohexanoic, decanoic, octadecanoic, acrylic,alphamethacrylic, crotonic, pentenoic, octenoic, octadecanoic, glycollicand others that will be readily apparent to those skilled in the artfrom the foregoing illustrative examples of radicals represented by R inFormula IV. Also, instead of using TMP tripropionate as a reactant withTMP as in Example 2, one can use any other triester of atrimethylolalkane that is represented by Formula VII, specific examplesof which are those wherein R in said formula are radicals derived fromthe above-named monocarboxylic acids. Additionally, instead of theparticular trimethylolalkanes employed in the foregoing examples, onecan use any other trimethylolalkane of the kind embraced by Formula III.Specific examples of such trimethylolalkanes will be obvious from theillustrative examples of radicals represented by R that were given inthe beginning of the specification.

Instead of benzene, any other inert, volatile, liquid, reaction mediumof which numerous illustrative examples were given hereinbefore, orother solvent, can be used.

The bicyclic ortho esters represented by Formula I are convertible tothe corresponding oxetane esters represented by Formula I-A. Theproduction of bicyclic ortho ester as hereinbefore described results inthe simultaneous production of some oxetane ester. When, for example,propionic acid is used in the practice of this invention, the proportionof oxetane ester produced is, for instance, approximately 17 weight (ormole) percent of the total ester (bicyclic and oxetane) product. Thus,when the yield of total ester is indicated as being, for example, molepercent this might more accurately be stated as 66.4 mole percent ofbicyclic ortho ester and 13.6 mole percent of oxetane ester.

It has been found that the isolated bicyclic ortho ester can berearranged, by heating, to the oxetane ester. For example, starting withrelatively pure orthopropionate and using a catalyst of alumina (e.g.,alundum), a 64 mole percent yield of TMP oxetane propionate wasobtained. It has further been discovered that the bicyclic ortho esterscan be prepared by way of a very facile acid-catalyzed rearrangement ofthe corresponding oxetane ester.

The several reactions described above may be illustrated by thefollowing equations:

CHz-O In carrying out the general reaction illustrated by Equation X(b)the bicyclic ortho ester is merely heated preferably in the presence ofan isomerization or rearrangement catalyst, at a temperature above about275 C., usually above about 300 C., e.g., within the temperature rangeof from about 325 C. to about 525 C.

EXAMPLE 13 Five (5) parts of TMP orthopropionate was heated at atemperature above 300 C. but below 500 C. in the 1 1 presence of a smallamount, more particularly about 0.4 part, of an alumina catalyst untilthere was obtained about 3.2 parts of the corresponding oxetane ester,which represents a 64% yield of TMP oxetane propionate.

In carrying out the general reaction illustrated by Equation X(c) theoxetane ester is merely warmed slightly above ambient temperature orheated at a materially higher temperature in the presence of a suitablerearrangement catalyst, e.g., a Bronsted or Lewis acid (acidic material)until substantially complete rearrangement to the ortho ester has beeneffected. Illustrative examples of the aforementioned catalysts that maybe used are H SO BF FCI A1Cl SnCl ZnCl TiCl or others known in the art.The temperature at which the oxetane ester is heated may range, forexample, between about 40 C. and about 100 C.

EXAMPLE 14 Three (3) parts of the oxetane ester produced as described inExample 13 was heated at 60 C. in the presence of a small amount, moreparticularly about 0.03 part, of sulfuric acid as catalyst untilcomplete rearrangement to the ortho ester was effected. Thus, the yieldof TMP ortho propionate was 100%.

The oxetane ester of Example 13 as well as other oxetane esters embracedby Formula I-A may be homopolymerized or used as a comonomer in makingbinary, ternary, quaternary or higher multi-component copolymers. Ifdesired, the homopolymer or copolymer may be subsequently orconcurrently hydrolyzed under acid or alkaline conditions to yield apolymer containing pendant functionally reactive hydroxyl groups. TakingTMP oxetane propionate as illustrative of the oxetane ester, thereaction may be illustrated by the following equations:

The different oxetane esters embraced by Formula I-A may becopolymerized with each other or one or more of them may becopolymerized with a large variety of other polymerizable monomers andother materials that are copolymerizable therewith including cyclicethers, e.g., epoxides, etc., lactones, e.g., beta-propiolactone, etc.;or they may be modified by reaction with other reactive materials, e.g.,monoand polyisocyanates, etc.

The polyol esters of this invention, both the bicyclic ortho and thepolyol oxetane esters, have unusual combinations of characteristics thatrender them especially valuable as chemical intermediates and in otherapplications. For instance, a polyol unsaturated ester, e.g., acrylate,of the kind embraced by Formula I or IA can be polymerized through theunsaturated ester portion of the molecule. Such polymerization may beeffected, for example, under anhydrous conditions and following thetechniques comrnonly employed or suggested for polymerizingpolymerizable unsaturated compounds, e.g., under heat, with or withoutthe aid of a free-radical (e.g., peroxy, azo, etc.) catalyst, an ioniccatalyst and/or other catalytic influences, e.g., ultraviolet light orionizing radiations, or by any other single or plurality of means. Thepolymer can 12 then be hydrolyzed, e.g., under acidic conditions using,for instance, an aqueous solution of sulfuric acid, to rupture the ringand to obtain a linear polymer having a backbone with -CH OH groupsattached to the different units of the linear chain. Such polymers (orcopolymers' of the polyol unsaturated ester which similarly can beproduced) can then be reacted with isocyanates, epoxides, aminoplasts(e.g., urea-formaldehyde, melamineformaldehyde, phenol-formaldehydepartial condensation products) and other compounds that are reactivewith methylol compounds to form a new class of polymeric materials thatare useful in coating, laminating, adhesive, molding, casting,impregnating, sealing and other applications.

EXAMPLE 15 This example illustrates another use as a chemicalintermediate of ortho esters embraced by Formula I.

TMP monopropionate was formed by adding TMP orthopropionate to an excessover the theoretical amount of water required for the desiredhydrolysis, which water contained a small amount of an acidic substance,specifically acetic acid as a catalyst. GC analysis showed completehydrolysis and a peak for only the monoester. The ortho ester thusprovides a convenient and economical way to obtain a polyol monoesterthat is free from contamination with di and triesters.

Instead of acetic acid any other organic or inorganic acid or acidicmaterial, especially those which are commonly used in hydrolysisreactions, may be employed. Among such acids may be mentioned sulfuric,hydrochloric, dichloroand trichloroacetic acids, difluoroandtrifluoroacetic acids and homologues of acetic acid, both substitutedand unsubstituted. I

The esters of this invention may also be used (in addition to thosementioned hereinbefore) as solvents, sequestering agents, modifiers ofnatural and synthetic resins, and for other purposes.

It will be understood, of course, by those skilled in the art that thepresent invention is not limited to the use of the specific ingredients,proportions thereof, temperature, time and other conditions of reactionthat are given in the foregoing detailed description and examples by wayof illustration.

The embodiments of the invention in which an exclusive property orprivilege is claimed are as follows:

1. The method of producing an oxetane ester represented by the generalformula where R represents an alkyl radical having 1 to 10 carbon atomsand R represents a number of the group consisting of hydrogen and alkylradicals having 1 to 10 carbon atoms, said method comprising isomerizingthe corresponding ortho ester by heating at a temperature above 275 C.but not higher than about 525 C. in the presence of an aluminaisomerization catalyst.

References Cited UNITED STATES PATENTS 2,910,483 10/1959 Schnell et a1260-333 3,000,901 9/1961 Wyler 260-333 3,105,838 10/1963 Luskin 260--3333,278,554 10/1966 Stark 260333 3,112,280 11/1963 Farthing 2603333,301,923 l/l967 Skovronek 260333 NORMA S. MILESTONE, Primary Examiner

